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mlock not working, variables getting cleared in function switch.

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as
as on 25 Aug 2020
Commented: Jan on 30 Aug 2020
M using Multiple function in a single '.m' file.
when i make a function call the previous data of the calling function is getting cleared.
Even if i use mlock then also data is getting cleared from in between function calls.
Is there any other method i can preserve variable and data of my main function.

  2 Comments

Geoff Hayes
Geoff Hayes on 25 Aug 2020
as - how are you storing the previous data? Is this data the output from calling this function before? Can you provide an example that demonstrates this problem?
as
as on 26 Aug 2020
function add(a,b)
mlock
c= a+b
d = subtract(a,b)
end
function k = subtract(e,f)
k = e-f;
end
Thank you Geoff Hayes .In above code when program reaches at ->k=e-f , variable c get destroyed even though i used mlock. If this is not correct use of mlock then please provide an example. What i want is to preserve variable c till the end of execution of function add() and in between call other function too.
In my script i'am loading a ROM.m file with lots of variable in it which i will be using in simulation, but when i call another function workspace is getting cleared.

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Answers (1)

Jan
Jan on 25 Aug 2020
Edited: Jan on 25 Aug 2020
Create this file:
function demo(In)
persistent v
switch lower(In)
case 'lock'
mlock
disp('locked')
case 'unlock'
munlock
disp('unlocked')
case 'set'
v = rand
case 'show'
v
end
end
Now run it:
demo('show') % v is []
demo('set')
clear('demo') % v is cleared
demo('show') % v is []
demo('set') % v is set to a value
demo('show') % v keeps its value
demo('lock')
clear('demo') % v is not cleared
demo('show') % v kept its value
demo('unlock')
clear('demo') % v is cleared
demo('show') % v is [] again
So usually declaring a variable as persistent is sufficient already and you need mlock only, if a brute program calls clear all (which is a bad programming pattern!).

  2 Comments

as
as on 26 Aug 2020
Thank you Jan, but here am loading a complete ROM file with lots of variable and their value, so i need to preserve that workspace for my entire run of that function and also call other function in between. Is it possible to load that ROM.m file as persistent?
Jan
Jan on 30 Aug 2020
Of course the workspaces are cleared,when a function is left, except if a variable is stored persistently. So just import the "ROM file" (what ever this means) into a variable, which is declared as persistent.

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